Condensed Consolidated Statement of Shareholders' Equity Statement - USD ($) $ in Thousands	Total	Class B Common Shares [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]
Total Shareholders’ Equity at Dec. 31, 2017	$ 423,294	$ 2	$ 9,304	$ 290,125	$ 187,999	$ 36,870	$ (101,006)
Stock Issued During Period, Value, Stock Options Exercised	(2,617)		(46)	(2,571)
Allocated Share-based Compensation Expense	(27)		0	(27)			0
Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition	(890)			30			920
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	1,456		67	2,873			(1,484)
Net Loss	(30,651)				(30,651)
Foreign currency translation adjustments	(11,622)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(11,622)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	1,568					1,568
Amortization of prior service costs and unrecognized gains (losses)	243
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(40,462)
Payments of Ordinary Dividends, Common Stock	(808)
Dividends, Common Stock, Cash	(808)
Total Shareholders’ Equity at Jun. 30, 2018	385,180	2	9,417	295,572	156,540	27,059	(103,410)
Total Shareholders’ Equity at Mar. 31, 2018	422,672	2	9,395	293,211	173,488	48,502	(101,926)
Stock Issued During Period, Value, Stock Options Exercised	(1,206)		(20)	(1,186)			0
Allocated Share-based Compensation Expense	(658)			(658)
Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition	(197)			(197)
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	548		2	2,030
Net Loss	(16,543)				(16,543)
Foreign currency translation adjustments	(23,438)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(23,438)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	1,705					1,705
Amortization of prior service costs and unrecognized gains (losses)	290
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax	290
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(37,986)
Payments of Ordinary Dividends, Common Stock	(405)
Dividends, Common Stock, Cash	(405)
Total Shareholders’ Equity at Jun. 30, 2018	385,180	2	9,417	295,572	156,540	27,059	(103,410)
Total Shareholders’ Equity at Dec. 31, 2018	359,147	2	9,419	297,919	142,447	12,793	(103,433)
Allocated Share-based Compensation Expense	651		29	970			(348)
Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition	211			211
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	2,581		140	2,953			(512)
Net Loss	(26,603)				(26,603)
Foreign currency translation adjustments	(3,984)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(3,984)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	1,037					1,037
Amortization of prior service costs and unrecognized gains (losses)	(75)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(29,625)
Convertible Debt Derivative Adjustments	(220)
Payments of Ordinary Dividends, Common Stock	(819)
Dividends, Common Stock, Cash	(819)
Total Shareholders’ Equity at Jun. 30, 2019	331,926	2	9,588	301,833	115,025	9,771	(104,293)
Total Shareholders’ Equity at Mar. 31, 2019	350,542	2	9,588	299,180	128,153	17,433	(103,814)
Allocated Share-based Compensation Expense	534		0	534			0
Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition	87			87
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	1,773		0	2,252			(479)
Net Loss	(12,717)				(12,717)
Foreign currency translation adjustments	(9,086)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(9,086)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	1,525					1,525
Amortization of prior service costs and unrecognized gains (losses)	(101)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(20,379)
Convertible Debt Derivative Adjustments	(220)			(220)
Payments of Ordinary Dividends, Common Stock	(411)
Dividends, Common Stock, Cash	(411)
Total Shareholders’ Equity at Jun. 30, 2019	$ 331,926	$ 2	$ 9,588	$ 301,833	$ 115,025	$ 9,771	$ (104,293)